1. Technical Field
The following description relates to one or more image readers.
2. Related Art
In a known method, an image reader having a one-dimensional image sensor reads, with the image sensor, images of a white reference member and a black reference member that are fixedly attached to a main body of the image reader, and determines a reference position (e.g., a central position) in a main scanning direction based on the read images.
After determining the reference position, the known image reader reads an image in the main scanning direction within an effective reading range, of an entire range physically readable by the image sensor in the main scanning direction, which effective reading range is defined as a partial range within a predetermined distance from the reference position in the main scanning direction.
According to the aforementioned technique, even though the image sensor has an individual difference, it does not cause a variation in the relative positional relationship between the effective reading range and the main body of the image reader.
Specifically, this kind of image sensor has an individual difference within a predetermined tolerance with respect to the position of the light receiving portion disposed inside the image sensor. Therefore, even though an exterior portion of the image sensor is accurately positioned relative to the main body of the image reader, it is not necessarily the case that a relative positional relationship between the light receiving portion and the main body of the image reader can be optimized.
In this respect, however, when the white reference member and the black reference member are fixedly attached to the main body of the image reader with a high positional accuracy, and the reference position is determined in the main scanning direction by actually reading the white reference member and the black reference member with the image sensor, it is possible to restrain a variation in the relative positional relationship between the effective readable range and the main body of the image reader.